1. Field of the Invention
The present invention relates to a nut and more particularly to a locking nut and a fastening structure consisting of the locking nut and a member being tightened.
2. Description of the Prior Art
Tightening and securing of a member by fastening a nut onto a male screw provided to the member is widely applied in assembling a variety of machine parts. It is noted, however, that between the male and the female screws fitted together a gap easily forms, so that the nut can be reversed and loosened with a light force.
Many proposals have been made to prevemt the loosening of the nut. They include, for example, a method which inserts a spring washer between the nut and the member being tightened, a method which tightens the nut and then deforms it by applying an external force to the nut, and a method that inserts a cotter pin into a hole cut through both the male screw and the nut.
Where the nut is subject to incessant large vibrations, like the ones used for fixing gears in automotive gear box, the spring washer is not sufficient in preventing the nut from becoming loose. The nut deforming method results in large variations in deformations and thus lacks quality stability. With the method of cutting a through-hole in the nut and the male screw, it is necessary to align the hole in the nut with the hole in the male screw, which may in turn make the tightening force become insufficient. Further, the formation of the through-hole reduces the strength of the male screw.